The show must go on! Trooper Cheryl Cole powers through illness at final London Girls Aloud gig.... by taking Madonna-style vitamin shot

There has been a lot of pressure on Girls Aloud - a massive reunion tour with dates across the country and an album to promote.

So perhaps when Cheryl Cole announced backstage she wasn't feeling too well, the rest of the members began to panic.

But in typical Cole style, the feisty brunette powered through the group's final night at the O2 - with a little help from a Madonna-style vitamin shot and by the online the reaction the girls more than impressed their loyal fan base.

Looking good! Cheryl powered through the show in style - if she hadn't mentioned her illness then audiences would be none the wiser

The five girls, who are touring the country as part of their Ten reunion, took to stage at London's O2 on Saturday evening looking as fierce as ever - with sizzling costumes which showed off their amazing figures and an array of their greatest hits.

Although sources at the concert told MailOnline Cheryl, 29, was fighting off an infection and despite getting a huge uplift from the crowd the brunette had taken an energy jab to get her through the gruelling show.

Powering through: Sources at the concert told MailOnline Cheryl was ill prior to the show - but she powered through the concert with style

Fierce! Cheryl and Nicola show off their curves in the revealing costumes to the delight of the crowds at the O2

He looks pretty happy with himself! One of Girls Aloud's backing dancers looks pretty pleased with himself that he landed this job

Cheryl, who has been linked to the vitamin injections before, certainly pulled off an energetic performance with onlookers saying they couldn't believe she was ill.

It is thought Cheryl took a B12 injection, which is similar to taking a vitamin tablet - but much more potent.

'Alcohol and stress deplete the body of vitamin B12,' Dr Martin Kinsella, who offers the jabs at his Cheshire clinic told MailOnline.

'If you don't have enough, you can feel low, rundown and lethargic. A quick shot of B12 can change that.'

She made a Promise to be there... and she was! Cheryl grins to crowds with Nadine, Kimberley and Sarah

She's an angel! Ever the performer Cheryl shrugged off illness to perform at the O2

Spread your wings! Sarah Harding looks right at home on stage

Some people, he added, have problems absorbing a vitamin in tablet form, but injecting into muscle - usually the bottom - gives a full dose, slowly released into the body over the weeks to follow.

As it is a water-soluble vitamin, once the body has used what is required, any excess is excreted in urine, making it virtually impossible to overdose.

Despite the quick fix solution to getting your energy back doctors warn people not to simply turn to the remedy if feeling tired or run down as it may mask underlying health problems.

Leggy ladies! Girls Aloud gave it their all at their last London gig

Jessica Rabbit: The girls took to the stage in ruby red dresses for a few numbers

Emotional: The girls held hands as they performed on of their songs

For the girls, completed by Kimberley Walsh, Nicola Roberts, Sarah Harding and Nadine Coyle, there was added pressure as they announced to crowds crews were filming for their celebratory tour DVD.

And crowds certainly seemed to love the show, with Twitter being set ablaze by tributes to the performance.